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martynhulsman avatar image
martynhulsman asked

1-Phase to 3-Phase will my design work?


Good day

I was hoping that someone would be able to assist me with this design.

I want to design a 3-Phase system, but only have a single phase municipal connection. The project will be done in to Phases. The first phase will be to supply the office building with Single phase, it will have a 15kVA victron with 16.5kWp PV and 40kWh battery storage (everything outside the blue dashed line). Later I want to add a 30kVA three phase system at the workshop to the same battery system, and add another 15kWp on the workshop and AC couple it with the 3-phase victrons. I will add 2 Cerbos for the single phase and three phase separately.

The single phase 15kVA Victron will be connected to the municipal grid and used to still supply the office building and charge the batteries if the PV is not enough.

Any help would be greatly appreciated.

Thank you.

1702296119477.jpeg


3 phase
1702296119477.jpeg (98.4 KiB)
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3 Answers
Alexandra avatar image
Alexandra answered ·

@martynhulsman

A few short notes.

You can't use ESS in a three phase system with one phase input.

Battery is too small.

And you can't share one battery in two systems.

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martynhulsman avatar image martynhulsman commented ·
@Alexandra thank you for the comment.

1. I run the 3-phase victron system only from the ESS not the single phase input. The single phase input only goes to the 15KVA victron that will supply the Office building.

2. Why is the battery too small? It has a 1C rating so only if you peak the inverters then it might be a problem. This is fixable by just upsizing the battery system, so it might be a good idea just to go for a Freedom Won 60/48 from the start.

3. Why can you not share a battery system? How will the BMS know if it is built into the Freedom Won that there are 2 system connected to it?

Hope to hear from you soon.

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Alexandra avatar image Alexandra ♦ martynhulsman commented ·

You very simply will not be able to load the ESS assistant onto a three phase with a single phase grid connection. You will find out when you program the system.


The picture you uploaded shows a FW 40/32. So too small for the design. It will fail. 15 + 10 + 10+ 10 (45kw) is way more than a 1C discharge especially if there is an overload/short-circuit.

FW have a recommendation battery sizing sheet. minimum size thamey will warranty on a system. Will be best to refer to that.

A shared battery bank is a definite no. Not if you want reliability and proper control. The BMS is not that clever.

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martynhulsman avatar image martynhulsman Alexandra ♦ commented ·
Hi @Alexandra, sorry for the late response.

I think what you are missing is that the 3ph system will only be connected to the battery bank. No where will it interact with the single phase connection (that is the purpose of having a forth inverter).

I did mention in my previous comment that I will upsize the battery, so that will not be a problem.

From what I can find online, it is very much possible to operate to different systems from 1 battery bank. You just have to make sure the battery is large enough.

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Alexandra avatar image Alexandra ♦ martynhulsman commented ·
Didn't miss it.

While people do bank share it is not best practice.

Your equipment you can do what you like.

But the shortfall will be - the battery can only control one system.


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Michelle Konzack avatar image
Michelle Konzack answered ·

How many kW do you get from the Grid?

The 15kVA inverter can charge with 200A, mean ~10kW and can do this 24 hours a day (=240kWh), if VERY WELL COOLED, otherwise it goes down.


First you have to know, how mzch energy you need for the office in 24h.


Lets say 100kWh, but then you have (in theorie) only 140kWh a day for the workshop.


Is this enough?


If you have only a singel phase connection to thr Grid and you need 3-phase system, then there is only ONE solution.

1) From the Grid you go to the 15kVA Inverter and power your office.

2) You need a huge 200kWh battery which will be charged from the Office Inverter

3) Install a SmartShunt and configure it as EnergyMeter for the three 10kVA inverters.


I would install AC coupled in the Workspace a GTI based 16kWp solarsystem, which will support your Workspace and take away the huge load from the three inverters and the Batteries.


However, it minght be, that the 15kVA office Inverter is to small, to charge the Batteries and support thr Office, hence I suggest you to put at least 2 parallel, but this depends on your Grid connection.


Mybe it is even better, if you use only one type of Charging-Inverter, e.G. Quattro 48/10000 and put in the office 2 parallel (max 4)


I have this year installed a similar (smaller system) using a pallet full of MultiPlus-II 48/5000 which where cheaper then bigger inverters.

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k-k avatar image
k-k answered ·

Make a one phase system as big as you need, or bigger for the future.

Think for what you really NEED 3 phases! Not for houshold but for a manufacture.

Motors, machines, robotics what ever. If you plan to ramp up a factory, just use a VFD for a new given machine. There are relative cheap industrial types by Siemens, ABB, Mitsubishi and many other namefull companies. It's no problem to find VFDs 1p230/3p400 from 0.375kW up to 100kW (and much more).

I think the best way to go offgrid with higher demands is using (De: BlockHeizKraftWerk - BHKW) chp/cogeneration in the winter and in the summer solar, having nice fat reserves.

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martynhulsman avatar image martynhulsman commented ·
Thank you for the comment.

Yes the 3-phase system will be used to operate some heavier machineries. The client would prefer a system that can handle the loads without adding more components to the system. The client will have to manage control and maintain those VSDs which I do not believe is in their interest.


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